Image forming apparatus

Abstract

To provide an image forming apparatus capable of suppressing the occurrence of process speed switching after the image forming preparation operation. [Solution] As part of the image formation preparation operation for the image formation job, the image forming unit operates according to the "user-specified speed" (S12). Simultaneously with the start of the image formation preparation operation, the media sensor starts detecting the sheet characteristics (S13). If the speed corresponding to the detected sheet characteristics matches the "user-specified speed," the image formation operation starts at the "user-specified speed" without switching the process speed of the image forming unit (S17). If the speed corresponding to the detected sheet characteristics does not match the "user-specified speed," the process speed of the image forming unit is switched and the image formation operation starts (S16, S17). This allows the user to avoid switching the process speed of the image forming unit by inputting the "user-specified speed."

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a printer, a copier, a facsimile machine, or a multifunction peripheral.

Background Art

[0002] An image forming apparatus develops an electrostatic latent image formed on a photoreceptor with toner, and transfers and fixes the developed toner image onto a sheet. The sheets are pre-set in a manual tray or a paper feed cassette, and are fed one by one from them to a conveyance path as an image forming job starts, and are conveyed by a conveyance unit to an image forming unit that forms an image on the sheets. The sheets may have different sheet characteristics such as thickness and surface properties, and the sheet characteristics are detected by a media sensor disposed in the conveyance path. Patent Document 1 proposes an image forming apparatus that sets image forming conditions including the operation speed of an image forming unit (conveniently referred to as a process speed) and the sheet conveyance speed of a conveyance unit based on the sheet characteristics detected by a media sensor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an image forming job, an image forming preparation operation (so-called, pre-rotation) required for forming an image on a sheet is started, and then an image forming operation for forming an image on the sheet is performed. At this time, if the process speed started in the image forming preparation operation is different from the process speed set by detecting the sheet characteristics by a media sensor, there is a possibility that a process speed switching may occur after the preparation operation.

[0005] This disclosure is made in view of the above-mentioned problems and aims to provide an image forming apparatus capable of suppressing the occurrence of process speed switching after the image forming preparation operation. [Means for solving the problem]

[0006] An image forming apparatus according to one embodiment of the present invention comprises: an image forming unit that forms an image on a recording material; a detection unit disposed upstream of the image forming unit with respect to the transport direction of the recording material and detecting the characteristics of the recording material; a control unit that controls the process speed, which is the speed at which the image forming unit is driven, based on the characteristics of the recording material detected by the detection unit; and an input unit that can receive information regarding the process speed of the image forming unit. The control unit, when detecting the recording material by the detection unit, starts the preparation operation of the image forming unit so as to drive the image forming unit at a first process speed based on the information input by the input unit. [Effects of the Invention]

[0007] According to this disclosure, it is possible to suppress the occurrence of process speed switching after the image formation preparation operation. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing the image forming apparatus of this embodiment. [Figure 2] A block diagram showing the control system of an image forming apparatus. [Figure 3] A schematic diagram showing the configuration of a media sensor. [Figure 4] A diagram illustrating the sheet size detection configuration. [Figure 5] (a) A diagram showing the initial media settings screen, (b) A diagram showing the settings selection screen, and (c) A diagram showing the sheet type input screen. [Figure 6] A flowchart illustrating the media setup process. [Figure 7] A flowchart illustrating the image formation process of this embodiment. [Figure 8]This diagram shows examples of user-specified speed input screens, including (a) input for starting speed, (b) input for the sheet to be used, and (c) input for the purpose of the sheet. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will now be described with reference to the drawings. Figure 1 is a schematic diagram showing the configuration of the image forming apparatus of this embodiment, and Figure 2 is a block diagram showing the control system for controlling the image forming apparatus. In the control system of the image forming apparatus, various other components may be connected to the control unit 300 in addition to those shown in Figure 2, but their illustration and description are omitted here as they are not relevant to the essence of the invention.

[0010] The control unit 300 shown in Figure 2 consists of a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, and an EEPROM (Electrically Erasable Programmable Read-Only Memory) 304. The CPU 301 controls the entire image forming apparatus 1 to form an image on a sheet by executing programs stored in the ROM 302 and EEPROM 304. In doing so, the CPU 301 can use the RAM 303 as a work area. Various types of sheet-like recording materials can be used as sheets, such as plain paper, cardboard, rough paper, textured paper, coated paper, plastic film, and cloth.

[0011] The image forming apparatus 1 includes an operation unit 330 capable of receiving user input. The operation unit 330 has an input unit 331 that allows the user to input various information, such as instructions to start a print operation on a sheet (referred to as an image forming job) and information regarding the process speed of the image forming unit 320, which will be described later, and a liquid crystal display 332. The liquid crystal display 332, which functions as a display unit, can display various information such as various programs, various data, or various screens, which will be described later. The operation unit 330 may also be a touch panel that accepts information input corresponding to the touch location in response to touch operations by the user on the screen displayed on the liquid crystal display 332. The CPU 301 can control the liquid crystal display 332 to display various screens.

[0012] The CPU 301 is capable of executing image forming jobs and starts printing operations in response to input of an input instruction to start an image forming job from an external device (not shown) or from the operation unit 330. The CPU 301 can drive and control the pre-fusing transport motor 145, the fuser motor 173, the post-fusing transport motor 146, the manual feed transport motor 147, the paper discharge transport motor 148, and the paper discharge transport motor 2 149, which are connected via the input / output interface (I / O) 307. In addition, the CPU 301 can detect input signals from the sheet transport sensor 171, the pre-cash register transport sensor 160, and the paper feed pickup sensor 152 via the input / output interface (I / O) 307.

[0013] Furthermore, the CPU 301 can detect input signals from the media sensor 280, sheet presence detection sensor 214, sheet width volume sensor 217, sheet sub-scan length detection sensor 1 218, and sheet sub-scan length detection sensor 2 219 via the input / output interface (I / O) 307. In addition, the CPU 301 can accept the start of image forming jobs input from the network interface (I / F) 314 and the fax interface (I / F) 315.

[0014] The CPU 301 has an image processing unit 316 that processes images corresponding to image forming jobs input from external devices (not shown) or the operation unit 330, and performs image processing such as image unfolding and rotation. The CPU 301 is also configured to control the image forming unit 320. The image forming unit 320 includes the process unit 120 shown in Figure 1, a transfer belt 130, a secondary transfer unit 140 having a pair of secondary transfer rollers, and a laser scanner unit 110. The CPU 301 can also control the temperature of the heater (not shown) of the fuser unit 170 shown in Figure 1. The scanner unit 101 can read the original document when making a copy.

[0015] Next, the basic operation of forming an image on a sheet will be explained using Figures 1 and 2. When an image forming job is started from the operation unit 330, the CPU 301 analyzes the print signal and starts the print operation. When the CPU 301 receives an instruction to transport a sheet from the paper feed cassette 150 which can hold sheets, it drives the pre-fixing transport motor 145 via the input / output interface (I / O) 307. As a result, the paper feed pickup roller 151 rotates, and the sheets loaded in the paper feed cassette 150, which acts as the loading unit, are transported one by one through the first transport path 410 to the common transport path 400. The CPU 301 then monitors whether the paper feeding operation from the paper feed cassette 150 has been performed normally using the paper feed pickup sensor 152.

[0016] When continuously transporting sheets from the paper cassette 150, the CPU 301 changes the paper feeding timing from the paper cassette 150 according to the sheet length of the sheet size (e.g., A4, B4, etc.) included in the start instruction for the image forming job, in order to improve the efficiency of sheet transport without causing paper jams. Sheet length refers to the length of the sheet in the transport direction.

[0017] Similarly, when the CPU 301 receives an instruction to convey a sheet from the manual tray 210 where sheets can be loaded, it drives the manual conveyance motor 147 via the input / output interface (I / O) 307. As a result, the manual pickup roller 211 rotates, and the sheets loaded in the manual tray 210 serving as the loading unit are conveyed one by one to the common conveyance path 400 via the second conveyance path 420. Then, the CPU 301 monitors whether the sheet feeding operation from the manual tray 210 is performed normally using the pre-registration conveyance sensor 160.

[0018] Based on the detection results of the sheet presence / absence detection sensor 214, sheet width volume sensor 217, sheet sub-scanning length detection 1 sensor 218, and sheet sub-scanning length detection 2 sensor 219 provided on the manual tray 210, the CPU 301 determines the sheet length before starting the sheet feeding operation. The CPU 301 can change the sheet feeding timing from the manual tray 210 according to the determined sheet length.

[0019] In the case of this embodiment, for the sheets conveyed from the manual tray 210 or the paper feed cassette 150, the media sensor 280 detects sheet characteristics such as the thickness and surface properties of the sheets. The media sensor 280 is arranged upstream of the image forming unit 320 with respect to the sheet conveyance direction, here, in the middle of the common conveyance path 400 where the first conveyance path 410 and the second conveyance path 420 merge. The media sensor 280 can detect the sheet characteristics while stopping the sheet conveyed from the manual tray 210 or the paper feed cassette 150 at the stop position for a predetermined detection time in the common conveyance path 400.

[0020] Based on the sheet characteristics detected by the media sensor 280, the CPU 301 can change image forming conditions such as the process speed, sheet conveyance speed, fixing temperature, transfer voltage, etc. The process speed is the speed at which the image forming unit 320 conveys the sheet while forming an image on the sheet, and includes the rotation speed of the rotating body (e.g., photosensitive drum, transfer belt, secondary transfer roller, etc.) of the image forming unit 320.

[0021] The CPU 301 starts the operation of the process unit 120 in accordance with the timing when the sheet arrives at the secondary transfer unit 140. The process unit 120 consists of a photosensitive drum, a developer, a charging roller, a photosensitive drum cleaner, etc. In the process unit 120, after the surface of the photosensitive drum is charged, an electrostatic latent image is formed on the photosensitive drum by a laser irradiated from the laser scanner unit 110. The electrostatic latent image formed on the rotating photosensitive drum is then developed on the photosensitive drum by toner in the developer. Subsequently, the toner image developed on the photosensitive drum is subjected to a primary transfer voltage in the primary transfer unit 121 and transferred to the transfer belt 130. The toner image transferred to the transfer belt 130 is then moved to the secondary transfer unit 140 by the rotation of the transfer belt 130.

[0022] Furthermore, the CPU 301 detects the position of the sheets transported by the transport rollers A153, B154, and C155 by monitoring the pre-cash register transport sensor 160. As an example of the transport section, the transport roller C155 transports the sheets transported from the paper feed cassette 150 and the manual feed tray 210, respectively, to the image forming unit 320 via the common transport path 400 where the first transport path 410 and the second transport path 420 merge.

[0023] Then, taking into account the timing when the leading edge of the sheet reaches the pre-cash register transport sensor 160, the transport of the sheet is controlled so that the leading edge of the sheet and the leading edge of the toner image on the transfer belt 130 coincide at the secondary transfer unit 140. For example, if the sheet arrives earlier than the toner image, the CPU 301 stops the sheet for a predetermined time using the pre-cash register transport roller 161 before resuming transport. In this way, the CPU 301 applies a secondary transfer voltage to the secondary transfer unit 140 to the sheet and toner image that have reached the secondary transfer unit 140, thereby transferring the toner image to the sheet.

[0024] After secondary transfer, the sheet is transported to the transport belt 190 and then to the fuser 170. In the fuser 170, the toner image on the sheet is heat-fixed to the sheet. The appropriate operating speed of the fuser 170 varies depending on the characteristics of the sheet being transported. The image forming unit 320 operates at a process speed that is preset to be approximately the same as the operating speed of the fuser 170. In this embodiment, the image forming unit 320 is capable of operating at a "standard speed" that can ensure fixation to sheets of a typical thickness (first thickness) and a "thick paper speed" that can ensure fixation to sheets thicker than the typical thickness. The "thick paper speed" is slower than the "standard speed". Note that the process speed is not limited to "standard speed" and "thick paper speed" and may be further subdivided.

[0025] Subsequently, when the leading edge of the fixed sheet, which has been transported downstream in the sheet transport direction, reaches the sheet transport sensor 171, the CPU 301 performs the following operation. Specifically, according to the content of the image forming job, the CPU 301 determines which transport path—sheet transport path A230, sheet transport path B231, or sheet transport path C234—to which the sheet being transported along the common transport path 400 should be transported by the transport roller 162, and switches the destination of the sheet by switching the transport flapper A172 and the transport flapper B182 according to the determination.

[0026] Specifically, when the image forming job is a double-sided print job or when the printed side is to be ejected to the output tray A200 with the printed side facing downwards, the CPU 301 switches the transport flapper A172 to transport the sheet to the sheet transport path A230. Also, when the image forming job is a single-sided print job or when the sheet is to be ejected to the output tray B196 or output tray C199 during double-sided printing, the CPU 301 switches the transport flapper B182 to transport the sheet to the sheet transport path B231. Finally, when the sheet is to be ejected to the output tray A200, the CPU 301 switches between the transport flappers A172 and B182 to transport the sheet to the sheet transport path C234.

[0027] The sheets transported to sheet transport path B231 are further transported downstream in the transport direction by transport roller E232. Subsequently, the sheets are transported to sheet transport path D181 and then to output tray B196 and output tray C199. The sheets transported to sheet transport path D181 are transported by output rollers F241, G242, and H243, which are driven by output transport motor 148. When CPU 301 wants to output a sheet to output tray B196, it switches flapper 183 to transport the sheet to transport path 193 and outputs the sheet to output tray B196. When CPU 301 wants to output a sheet to output tray C199, it switches flapper 183 to transport path 184. Next, the CPU 301 uses the paper output rollers I244, J245, and K246, driven by the paper output transport motor 149, to transport the sheets to the transport path 184 and eject them into the paper output tray C199.

[0028] When printing on one side and ejecting the printed side downwards to the output tray A200, the sheet moves along the sheet transport path A230, and when the trailing edge of the sheet passes the reversal roller 163, the CPU 301 reverses its drive towards the output roller 180 and ejects the sheet to the output tray A200.

[0029] During double-sided printing, the sheet proceeds to the sheet transport path A230 and is then transported to the double-sided reversal transport path D233 by double-sided transport rollers A164, B165, C166, D179, and E168. Next, when the trailing edge of the sheet passes double-sided transport roller D179, the double-sided reversal flapper 178 is switched to the side of double-sided transport roller F169, and the drive is reversed. Subsequently, the sheet is transported by double-sided transport rollers F169, G175, H176, and I177 and handed over to transport roller C155. When the image forming job is completed, the CPU 301 displays completion to the operation unit 330.

[0030] An image forming job is a series of operations for forming an image on a sheet based on a print signal. It refers to the entire process from the start of the preparatory operations necessary for image forming (so-called pre-rotation), through the image forming operations that create the image on the sheet, to the completion of the preliminary operations necessary to finish image forming (so-called post-rotation).

[0031] <Media Sensor> Next, the media sensor 280, which acts as a detection unit for detecting sheet characteristics such as sheet thickness and surface properties, will be explained using Figure 3. As shown in Figure 3, the media sensor 280 has a media sensor main unit 54 and an external LED (light-emitting diode) 55b. The media sensor main unit 54 has an LED 55a as a light source, a phototransistor 56a, and a phototransistor 56b within the unit.

[0032] <Sheet surface texture detection> First, the method for detecting the surface properties of the sheet using the media sensor 280 will be explained. Light emitted from the LED (light-emitting element) 55a passes through the slit 57a and the upper window provided in the sheet transport guide 40, and is irradiated onto the surface of the sheet P as it is transported along the common transport path 400 while being guided by the sheet transport guide 40. The reflected light from the sheet P passes through the slits 57b and 57c and is received by the phototransistors 56a and 56b (light-receiving elements). Phototransistor 56a receives a portion of the diffusely reflected light emitted from the LED 55a and reflected from the surface of the sheet P, and outputs a diffuse reflection output value. Phototransistor 56b receives the specularly reflected light emitted from the LED 55a and reflected from the surface of the sheet P, and outputs a specular reflection output value. The surface property value x is calculated by Equation 1 shown below. Surface quality value x = Specular reflection output value / Diffuse reflection output value ... (Equation 1)

[0033] Equation 1 utilizes the characteristic that the smoother and finer the surface of sheet P, the easier it is to specularly reflect light. A calculation device (not shown) located on the media sensor 280 quantifies the surface properties of sheet P using Equation 1 and sends the calculated surface property value x to the CPU 301. The CPU 301 uses the received surface property value x and a threshold value for determining surface properties to determine the surface properties of sheet P. If the surface property value x is greater than the threshold value, the CPU 301 determines that the surface properties of sheet P are smooth and fine. If the surface property value x is less than or equal to the threshold value, the CPU 301 determines that the surface properties of sheet P are rough and coarse. Here, one threshold value is used to detect two types of sheet surface properties, but multiple threshold values ​​may be used to further subdivide and detect them.

[0034] <Sheet thickness detection> Next, the method for detecting the sheet thickness using the media sensor 280 will be described. The sheet transport guide 40 is provided with a lower window for irradiating light from the back side of the sheet P. Light emitted from the external LED (light-emitting element) 55b passes through the light-gathering guide 57d and the lower window to irradiate the back side of the sheet P. The transmitted light from the sheet P passes through the upper window and the slit 57b to be received by the phototransistor 56a. The phototransistor 56a receives the positively transmitted light emitted from the external LED 55b and transmitted through the sheet P and outputs a positively transmitted output value. The positively transmitted output value detected by the phototransistor 56a is sent to the CPU 301.

[0035] The CPU 301 determines the thickness of sheet P using the transmitted positive transmission output value and a threshold value for determining the thickness. In this embodiment, thresholds A and B are used to make three types of distinctions: "thick," "normal," and "thin" (threshold A < threshold B). If the positive transmission output value is less than or equal to threshold A, the CPU 301 determines that the thickness of sheet P is "thin." If the positive transmission output value is greater than threshold A and less than or equal to threshold B, the CPU 301 determines that the thickness of sheet P is "normal." If the positive transmission output value is greater than threshold B, the CPU 301 determines that the thickness of sheet P is "thick." In this embodiment, the operating speed of the fuser 170 and the process speed (second process speed) of the image forming unit 320 are set to "standard speed" (first speed) when sheet P is determined to be "thin" or "normal" (first thickness), and to "cardboard speed" (second speed) when sheet P is determined to be "thick" (second thickness). As mentioned above, "cardboard speed" is slower than "standard speed."

[0036] In this embodiment, two thresholds are used, but one threshold may be used, or three or more thresholds may be used to determine a more finely subdivided thickness. Also, in this embodiment, an optical sensor is used for the media sensor 280, but it is not limited to this, and other types of sensors such as ultrasonic sensors may be used as long as they can detect surface properties or thickness.

[0037] <Sheet size detection> Next, the sheet size detection configuration for sheets set in the manual feed tray 210 will be explained using Figure 4. Note that the same detection configuration may be used for the paper feed cassette 150, so the explanation will be omitted here. As shown in Figure 4, the manual feed tray 210 is equipped with a manual feed pickup roller 211 and sheet side regulating guides 212 and 213. Sheets set in the manual feed tray 210 are held in place by the sheet side regulating guides 212 and 213, preventing the sheets from being transported at an angle when they are separated and transported by the manual feed pickup roller 211. The sheet side regulating guides 212 and 213 are slidable in the direction of arrows 215 and 216 in the figure, so that even if sheets of different widths are set, the sheets can be prevented from becoming skewed.

[0038] The manual feed tray 210 is also equipped with a sheet presence detection sensor 214, a sheet width volume sensor 217, a sheet sub-scan length detection sensor 1 218, and a sheet sub-scan length detection sensor 219. The sheet presence detection sensor 214 is provided to detect whether or not a sheet is loaded in the manual feed tray 210. When a sheet is set on the manual feed tray 210, the sheet presence detection sensor 214 turns on, and an on signal is input to the CPU 301 from the sheet presence detection sensor 214, causing the CPU 301 to determine that there is a sheet in the manual feed tray 210. When no sheet is set on the manual feed tray 210, the sheet presence detection sensor 214 turns off, and an off signal is input to the CPU 301 from the sheet presence detection sensor 214, causing the CPU 301 to determine that there is no sheet in the manual feed tray 210.

[0039] The sheet width volume sensor 217 is connected to the sheet side regulating guides 212 and 213 via a link member (not shown). Therefore, the sheet width volume sensor 217 outputs a signal (AD value) to the CPU 301 corresponding to the position of the sheet side regulating guides 212 and 213 in conjunction with the operation of the sheet side regulating guides 212 and 213. The CPU 301 detects the sheet width based on the signal (AD value) output from the sheet width volume sensor 217. Here, the sheet width is the length in the width direction intersecting the sheet transport direction (main scan length). In contrast, the sheet sub-scan length detection sensor 1 218 and the sheet sub-scan length detection sensor 2 219 have, for example, a flag-type configuration and detect the transport direction length (sub-scan length) of the sheet set on the manual feed tray 210. In this way, the manual feed tray 210 is configured to automatically detect the sheet size, including the main scan length and sub-scan length, for the sheet that is set on it.

[0040] <Initial media settings screen> In this embodiment, when a sheet is detected in the manual feed tray 210 (or paper feed cassette 150, hereafter the same), the "Media Setup Initial Screen" is displayed on the liquid crystal display 332. Figure 5(a) shows the "Media Setup Initial Screen". The "Media Setup Initial Screen" is a screen displayed to allow the user to set whether or not to perform automatic detection of sheet characteristics by the media sensor 280.

[0041] As shown in Figure 5(a), the "Media Settings Initial Screen" displays the sheet detection size 503 of the sheet set in the manual feed tray 210. The sheet detection size 503 is displayed based on the main scan length, which is determined by the detection result of the sheet width volume sensor 217, and the sub-scan length, which is determined by the detection results of the sheet sub-scan length detection sensor 1 218 and the sheet sub-scan length detection sensor 2 219. For example, if the main scan length is "210 mm" and the sub-scan length is "297 mm", "A4 Portrait" will be displayed in the sheet detection size 503, and if the main scan length is "257 mm" and the sub-scan length is "182 mm", "B5 Landscape" will be displayed in the sheet detection size 503. Although not explained here, the user can also manually input the size of the sheet set in the manual feed tray 210.

[0042] Furthermore, the "Initial Media Settings Screen" displays a "Change Sheet Type" button 501 and an "OK" button 550. When the "Change Sheet Type" button 501 is pressed, the "Settings Selection Screen" is displayed on the LCD display 332. Figure 5(b) shows the "Settings Selection Screen". As shown in Figure 5(b), the "Settings Selection Screen" displays a "Automatically Detect During Printing" button 511 and a "Select from List" button 512. The "Automatically Detect During Printing" button 511 is used by the user to set the automatic detection of sheet characteristics by the media sensor 280.

[0043] The "Select from List" button 512 is a button for the user to manually input the sheet type. When the "Select from List" button 512 is pressed, the "Sheet Type Input Screen" is displayed on the liquid crystal display 332. Figure 5(c) shows the "Sheet Type Input Screen". The "Sheet Type Input Screen" is a screen for inputting information about multiple sheet types, and as shown in Figure 5(c), the sheet types are displayed in a list to prompt the user to input the sheet type. Here, the sheet types (thin paper 1, plain paper 1, etc.) are displayed along with their basis weight. The control unit 300 stores the sheet type selected by the user from the list in the RAM 303.

[0044] <Media setup process> Figure 6 is a flowchart of the "media setup process" using the "initial media setup screen" described above. The "media setup process" is started by the control unit 300 (specifically the CPU 301) when the power of the image forming apparatus 1 is turned on. As shown in Figure 6, the control unit 300 determines whether or not a sheet is set in the manual feed tray 210 based on the detection result (on signal or off signal) sent from the sheet presence detection sensor 214 (S1). If no sheet is set in the manual feed tray 210 (NO in S1), the control unit 300 repeatedly executes the process in step S1. If a sheet is set in the manual feed tray 210 (YES in S1), the control unit 300 displays the "initial media setup screen" (see Figure 5(a)) on the liquid crystal display 332 (S2).

[0045] Then, the control unit 300 determines whether the user has pressed the "Change Sheet Type" button 501 on the "Initial Media Settings Screen" (S3). If the "Change Sheet Type" button 501 has not been pressed (NO in S3), the control unit 300 determines whether the user has pressed the "OK" button 550 on the "Initial Media Settings Screen" (S4). If the "OK" button 550 has not been pressed (NO in S4), the control unit 300 returns to the process in step S3. If the "OK" button 550 has been pressed (YES in S4), the control unit 300 terminates the "Media Settings Process".

[0046] If the "Change Sheet Type" button 501 on the "Initial Media Settings Screen" is operated (YES in S3), the control unit 300 displays the "Setting Selection Screen" (see Figure 5(b)) on the liquid crystal display 332 (S5). After the "Setting Selection Screen" is displayed, the control unit 300 determines whether the "Automatically Detect During Printing" button 511 on the "Setting Selection Screen" has been operated by the user (S6). If the "Automatically Detect During Printing" button 511 has been operated by the user (YES in S6), the control unit 300 proceeds to step S9. If the "Automatically Detect During Printing" button 511 has been operated by the user, the control unit 300 automatically detects the sheet characteristics of the first sheet transported from the manual feed tray 210 using the media sensor 280.

[0047] If the "Automatically detect during printing" button 511 on the "Settings Selection Screen" is not pressed by the user (NO in S6), the control unit 300 determines whether the "Select from list" button 512 on the "Settings Selection Screen" has been pressed by the user (S7). If the "Select from list" button 512 has not been pressed by the user (NO in S7), that is, if the "OK" button 551 on the "Settings Selection Screen" has been pressed, the control unit 300 returns to the process in step S6. On the other hand, if the "Select from list" button 512 has been pressed by the user (YES in S7), the control unit 300 displays the "Sheet type input screen" (see Figure 5(c)) on the liquid crystal display 332 (S8).

[0048] The control unit 300 determines whether the user has pressed the "OK" button 551 on the "Settings Selection Screen" or the "OK" button 553 on the "Sheet Type Input Screen" (S9). If the user has pressed the "OK" button 552 on the "Settings Selection Screen" or the "OK" button 553 on the "Sheet Type Input Screen" (YES in S9), the control unit 300 returns to the process in step S2 and redisplays the "Media Settings Initial Screen" (see Figure 5(a)) on the liquid crystal display 332 (S2).

[0049] On the other hand, if the user has not pressed the "OK" button 551 on the "Settings Selection Screen" or the "OK" button 553 on the "Sheet Type Input Screen" (NO in S9), the control unit 300 returns to the process in step S6. In this case, even if the user has pressed the "Automatically detect during printing" button 511 on the "Settings Selection Screen," the control unit 300 will not perform automatic detection of sheet characteristics by the media sensor 280 during the image forming job. Also, even if the user has selected any of the sheet types from the list displayed on the "Sheet Type Input Screen," the user-selected sheet type will not be stored in the RAM 303.

[0050] <Image Formation Processing> Next, the "image forming process" of this embodiment will be explained using Figures 7 and 8(c) with reference to Figure 2. The "image forming process" shown in Figure 7 is executed by the control unit 300 (specifically the CPU 301) in response to the input of an instruction to start an image forming job when the "Automatic detection during printing" button 511 (see Figure 5(b)) is operated by the user. In the following explanation, the manual feed tray 210 will be used as an example, but the same may apply to the paper feed cassette 150.

[0051] As shown in Figure 7, the control unit 300 acquires the "user-specified speed" (S11). In this embodiment, before the start of the image forming job, the user can input the "user-specified speed" according to the "user-specified speed input screen" displayed on the liquid crystal display 332. The "user-specified speed" here refers to information regarding the process speed of the image forming unit 320. Figures 8(a) to 8(c) show examples of the "user-specified speed input screen". The "user-specified speed input screen" displays information regarding the process speed to prompt user input.

[0052] <User-specified speed input screen> Figure 8(a) shows a screen that directly displays "User-Specified Speed" as one of several process speed options. The screen shown in Figure 8(a) displays "Standard Speed" button 701 and "Cardboard Speed" button 702 as options. When the user operates the "Standard Speed" button 701, "Standard Speed" is entered as the "User-Specified Speed" and stored in RAM 303 (see Figure 2). On the other hand, when the user operates the "Cardboard Speed" button 702, "Cardboard Speed" is entered as the "User-Specified Speed" and stored in RAM 303.

[0053] Figure 8(b) shows a screen displaying multiple "sheet types" with different characteristics, commonly used for sheets whose sheet characteristics are detected by the media sensor 280. The screen shown in Figure 8(b) displays "normal paper" button 711 and "high-quality paper" button 712 as sheet types. When the user operates the "normal paper" button 711, "standard speed" is entered as the "user-specified speed" and stored in RAM 303. On the other hand, when the user operates the "high-quality paper" button 712, "thick paper speed" is entered as the "user-specified speed" and stored in RAM 303. Generally, thick paper with high hardness is used for sheets whose sheet characteristics are detected by the media sensor 280, and since thick paper is expensive, buttons are displayed so that the user can input according to their price perception.

[0054] Figure 8(c) is a screen displaying multiple "sheet usages" with different characteristics, commonly used for sheets whose sheet characteristics are detected by the media sensor 280. The screen shown in Figure 8(c) displays "Internal Use" button 721 and "External Distribution" button 722 as usages. When the user operates the "Internal Use" button 721, "Standard Speed" is entered as the "User-Specified Speed" and stored in RAM 303. On the other hand, when the user operates the "External Distribution" button 722, "Cardboard Speed" is entered as the "User-Specified Speed" and stored in RAM 303. Generally, thick, high-quality paper is used for sheets that form images for distribution to external parties, and such paper is used for sheets whose sheet characteristics are detected by the media sensor 280. Therefore, buttons are displayed so that the user can input according to the sheet's usage.

[0055] Returning to the explanation of Figure 7, the control unit 300 starts the image forming unit 320 at a process speed of "user-specified speed" as an image forming preparation operation before the media sensor 280 starts detecting the sheet characteristics (S12). Then, the control unit 300 starts the sheet characteristics detection operation by the media sensor 280 (S13). That is, the control unit 300 feeds the first sheet from the manual feed tray 210, transports it to the media detection position of the media sensor 280, and when the sheet reaches the media detection position, temporarily stops the transport and performs sheet characteristics detection by the media sensor 280.

[0056] The control unit 300 then determines whether the detection of sheet characteristics by the media sensor 280 has finished (S14). This completion determination can be made by determining whether a predetermined detection time (e.g., 1000ms) has elapsed since the sheet stopped. The control unit 300 waits until the detection of sheet characteristics is finished (NO in S14). After the detection of sheet characteristics is finished (YES in S14), the control unit 300 determines whether the speed corresponding to the sheet characteristics detected by the media sensor 280 matches the "user-specified speed" (S15). Here, "match" means that the speed corresponding to the detected sheet characteristics is within a range of, for example, "±2%" of the "user-specified speed".

[0057] If the speed corresponding to the detected sheet characteristics (second process speed) does not match the "user-specified speed" (first process speed) (NO in S15), the control unit 300 switches the process speed of the image forming unit 320 from the "user-specified speed" to the speed corresponding to the sheet characteristics (S6) and starts the image forming operation (S17). For example, if the "user-specified speed" is "cardboard speed" and the speed corresponding to the detected sheet characteristics is "standard speed", the control unit 300 switches the process speed of the image forming unit 320 from "cardboard speed" to "standard speed". The control unit 300 starts the image forming operation after the switching time required for the process speed of the image forming unit 320 to reach the speed corresponding to the detected sheet characteristics has elapsed. That is, the control unit 300 sequentially feeds the second and subsequent sheets from the manual feed tray 210 and causes the image forming unit 320, which is operating at the "standard speed" after the switch, to form an image.

[0058] On the other hand, if the speed corresponding to the detected sheet characteristics matches the "user-specified speed" (YES in S15), the control unit 300 starts the image formation operation at the "user-specified speed" without switching the process speed of the image forming unit 320 to the speed corresponding to the detected sheet characteristics (S17). For example, if the "user-specified speed" is "cardboard speed" and the speed corresponding to the detected sheet characteristics is also "cardboard speed", the control unit 300 starts the image formation operation without switching the process speed of the image forming unit 320 from "cardboard speed". That is, the control unit 300 sequentially feeds the second and subsequent sheets from the manual feed tray 210 and causes the image forming unit 320, which is operating at "cardboard speed", to form an image. In this way, the control unit 300 can start the image formation operation without switching the process speed of the image forming unit 320, which was operating at the "user-specified speed" during the image formation preparation operation.

[0059] As described above, in this embodiment, when an image forming job is executed, the image forming unit 320 operates according to the "user-specified speed" input as an image forming preparation operation, and the media sensor 280 detects the sheet characteristics. If the speed corresponding to the detected sheet characteristics matches the "user-specified speed," the image forming operation starts at the "user-specified speed" without switching the process speed of the image forming unit 320. On the other hand, if the speed corresponding to the detected sheet characteristics does not match the "user-specified speed," the process speed of the image forming unit 320 is switched and the image forming operation starts.

[0060] According to this, if the user knows in advance that the sheet is the type that will trigger a process speed switch based on the detection of sheet characteristics by the media sensor 280, the process speed switch of the image forming unit 320 can be prevented by having the user input a "user-specified speed" in advance. In other words, conventionally, even if the user knew that the sheet would trigger a process speed switch, it was not possible to avoid the process speed switch. In contrast, in the present invention, if the user knows in advance that the sheet will trigger a process speed switch, the process speed switch can be prevented by inputting a "user-specified speed" corresponding to the detected speed and starting the image forming preparation operation at the "user-specified speed". Therefore, the wear and tear on the image forming unit 320 caused by the process speed switch that occurred conventionally can be suppressed.

[0061] In the above-described embodiment, the media sensor 280 was described as being located in the middle of the common transport path 400, but it is not limited to this. For example, the media sensor 280 may be located in the first transport path 410 through which sheets from the paper feed cassette 150 are transported, or in the second transport path 420 through which sheets from the manual feed tray 210 are transported. [Explanation of symbols]

[0062] 1…Image forming apparatus, 155…Transportation unit (transport roller C), 210 (150)…Loading unit (manual feed tray, paper feed cassette), 280…Detection unit (media sensor), 300…Control unit, 320…Image forming unit, 331…Input unit, 332…Display unit (liquid crystal display), P…Recording material (sheet)

Claims

1. An image forming unit that forms an image on the recording material, A detection unit is positioned upstream of the image forming unit in the direction of transport of the recording material and detects the characteristics of the recording material. A control unit controls the process speed, which is the speed at which the image forming unit is driven, based on the characteristics of the recording material detected by the detection unit. It includes an input unit that can input information regarding the process speed of the image forming unit, When the control unit detects the recording material using the detection unit, it initiates the preparatory operation of the image forming unit so as to drive the image forming unit at a first process speed based on the information input by the input unit. An image forming apparatus characterized by the following features.

2. The control unit, after the detection of the recording material by the detection unit is completed, If the second process speed, which corresponds to the characteristics of the recording material detected by the detection unit, does not match the first process speed, the system switches from the first process speed to the second process speed. If the second process speed matches the first process speed, no switching from the first process speed to the second process speed is performed. The image forming apparatus according to feature 1.

3. A loading section for loading recording materials, The system includes a transport unit that transports the recording material loaded in the loading unit to the image forming unit, The detection unit detects the characteristics of the recording material while the recording material being transported by the transport unit is stopped at the stop position. The image forming apparatus according to feature 1.

4. Equipped with a display unit capable of displaying information, The display unit displays information regarding the process speed to prompt the user for input. The image forming apparatus according to feature 1.

5. The display unit displays, as information regarding the process speed, one of the following: a plurality of process speed candidates, a plurality of recording material types with different recording material characteristics, or a plurality of recording material applications with different recording material characteristics. The image forming apparatus according to feature 4.

6. The control unit sets the second process speed to a first speed when the recording material has a first thickness, and to a second speed slower than the first speed when the recording material has a second thickness that is thicker than the first thickness, according to the detection result by the detection unit. The image forming apparatus according to feature 2.

7. The aforementioned loading section is a manual feed tray. The image forming apparatus according to feature 3.

8. The aforementioned loading section is a paper feed cassette. The image forming apparatus according to feature 3.

Images